Interesting mail comes in. A lot of it positive. A good few brickbats.

Here's one of the latter. Hugh, he says, you mention a rant by a white woman on a tram, but fail to mention four black Somalian women racially abusing two white people "and still walking the streets. Is this the tolerance you want? How do you sleep at night."

The answer to that is: variably, but stuff like this doesn't keep me awake. In the tram case, the prosecution alleges racial aggravation. In the other case, it did not. Still, I know where he is coming from. It's the hardy perennial that says everyone makes a fuss if a white person racially assaults a black person but no one cares when the roles are reversed.

Is it really the case that the media ignores racist crime in which white people are the victims and minorities the perpetrators? Hardly. It's part of the "we're the oppressed minority now" zeitgeist that fuels the rightwing blogs and excites the commentators. Why would anyone keep them quiet?

Turn to Google. White victim, Asian suspects, Lancashire Telegraph in April: "Gang attack on Burnley teenagers"; white victim, Asian suspect, BBC Online in July: "Glasgow Queen's Park shooting was 'racially motivated'"; the Telegraph: "White man subjected to race attack by gang of yobs" (suspects Asisn); headline in the Mail for the same story: "Father-of-two beaten up and left for dead by Asian gang for being white." None of it a secret.

For all that, this juxtaposition of crime and ethnicity can be interesting. Witness the view expressed by one of the guys interviewed in the Guardian's Reading the Riots project. If there is going to be a murder, he said, better for a black person to be murdered by another black person than a white one. Neither is right, he said, but a black person killing another black person will usually occur for commercial reasons or as the side product of a criminal enterprise. By contrast, "if a white person was to do a black person, something ... you ... you would feel it ... you would get angry, for the fact that the whole slavery thing happened, and it's like it's all gonna come back again." Absurd. But once melanin becomes the issue, the absurdities never end.

• This article was amended on 15 December 2011 because the original incorrectly referred to melatonin.